Fix #306 - Retrieve parentId by realm name

[TuningYourCode]

This change will fix #306 as it will try to retrieve the uuid of the given realm first and pass it as parentId.

It is a quiet similar solution like in https://github.com/treydock/puppet-module-keycloak/blob/master/lib/puppet/provider/keycloak_ldap_mapper/kcadm.rb#L127

[treydock]

@TuningYourCode Can you please rebase this PR against this repo's master branch? There was a recently merged fix that's needed to get tests passing

[treydock]

The unit tests here need updates:

puppet-module-keycloak/spec/unit/puppet/provider/keycloak_ldap_user_provider/kcadm_spec.rb

Line 52 in 1795982

describe 'create' do

Might be just

allow(resource.provider).to receive(:get_parent_id).with('test').and_return('test')

[TuningYourCode]

Thanks for the fix - didn't had time yet to look at it :)